Compressor-cooling system



Jan. 22; 1929.

B. S. AIKMAN COMPRESSOR COOLING SYSTEM [fir/612227 5%!"757? 5 12 11117224222 M W Filed April! 5, 1927 Patented Jan. 22, 1929.

UNITED STATES PATENT OFFICE.

BURTON S. AIKMAN, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO NATIONAL BRAKE &. ELECTRIC COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

COMPRESSOR-COOLING SYSTEM.

Application filed April 5,

My invention relates to air compressors and more specifically to a novel method of and means for cooling the same.

There has been an insistent demand in the art for a compressor of small size and large capacity. This demand has been precipitated by the recent work in air brakes for dirigible vehicles, such as busses, trucks, and the like. In that art the weight that can be carried must be limited and yet capacity for all demands must be provided. To meet this requirement it has been attempted to drive compressors of standard design at greater shaft speeds, but two chief difficulties have arisen; first, drop in volumetric efficiency due to imperfect valve action, and, second, overheating with consequent danger of destruction due to failure of lubrication. As a result, the greatly lowered over-all efiiciency of such a compressor at high speed has made the proposal impracticable.

In my prior Patent No. 1,611,866, I disclose and claim a compressor employing a sleeve intake valve actuated by ring friction to give rapid intake valve action with adequate opening. At the same time, I provide therein air cooling, scavenging, and super-charging of the cylinder. I found that this type of valve action could be operated with complete success at much higher speed than was possible with conventional poppet valve designs.

This valve arrangement I have found disposed of the difficulty of loss of volumetric eiiiciency at high speed for failure to take in an adequate charge upon each intake stroke. However, I discovered that with the conventional type of discharge check valve and chamber and discharge passageways in the head, the hot gas in contact with the upper side of the head caused a conduction of heat from the hot compressed gas to the wall of the'chamber, which was formed in part by the head and in part by walls themselves in conducting relation to the head. Hence, although. the compressor could operate at higher speed, it required water cooling for continuous operation at such speed. Thereupon, I devised the improvement which is shown and claimed in my co-pending Patent No. 1,632,262, wherein the discharge check valve chamber and the passageway beyond the same in which hot compressed air or a gas is retained were removed from thermal conductivity by the inter-position upon the top of the head and upon said neck the compres- 1927. Serial No. 181,104.

sor could be operated at higher speeds and for much longer periods than had previously been possible and with less tendency to over heat, even when air cooling only was relied upon.

I found, however, that upon full motor speed and with a permissible amount of air cooling, there was still a tendency to over heat, which resulted from the return of heat from the hot gas beyond the discharge check valve to the walls of the chamber. The neck construction of my co-pcnding patent limits the return of heat by conduction, but since this structure for practical reasons is preferably made of cast iron, there is still on continuous operation at high speed a very considerable return of heat by conduction and radiation which is undesirable. This could be tolerated, so far as the compressor head and cylinder are concerned if it. did not affect the discharge valve or carbonize the oil on the walls of the chamber or in the chamber. I find from my experiments that the heat of the gases tends to carbonize oil carried over in the discharge from the cylinder and causes a deposit upon the check valve and walls of the chamber, tending to cause leakage thereby, and also the. hot gases tend to injure the structure of the valve, causing in some cases warpage and even breakage of the valve as a result. The carbon deposit and warpage cause leakage of the valve which tends further to building up of the temperature.

The present improvement has been devised to rid the valve of the heat of the compressed gases received from the cylinder at each stroke. Primarily, what I have done in the present improvement is, first, to dilute each charge of hot gas discharged from the cylinder with colder gas and then provide for cooling the mixture by taking heat therefrom.

In the normal operation of the device under load, there is a flow of compressed air from the mass being cooled, but the mass acts as a pool into which the hot charges of gas are stirred and mixed. This mass or pool has sufficient radiating and heat dissipating ability that it never rises to a dangerous temperature and, hence, the menace of carbonization of the oil and injury to the discharge check valve is avoided. As a result, I have a compressor which may now be operated indefinitely at full motor speed with only air cooling.

structurally, I secure this result in the form herein illustrated by opening the discharge check valve chamber directly and freely into a tank of large relative volume which has suflicient radiating surface to dissipate the required amount of heat. I have since improved both the structure and method of operation, as shown in my co-pending application Serial No. 18O, l33, filed April 2, 1927, which contains broad claims to the common invention. The present invention provides a further system of internal cooling by the use of a body of liquid, preferably water, which may, or may not, be employed.

New in order to acquaint those skilled in the art with the manner of constructing and operating a device embodying my invention, I shall describe in connection with the accompanying drawings a specific embodiment of the same.

In the drawings Figure 1 is a side view partly in section showingan embodiment of the invention; and

Figure 2 is an enlarged fragmentary section. showing the top of the compressor and the discharge check valve in section.

The compressor 1 is mounted upon a base plate 2 which also supports the driving motor 3, this driving motor being connected in this case to the compressor 1 through the intermediary of a belt drive comprising a belt l running over the motor pulley 5 and the fiy-whcel 6 of the air compressor, which flywheel has spokes formed in the shape of air 13101 e lin vanes or fans 7 to drive air against the cylinder and crank-case of the compressor.

I do not wish to be restricted to a belt drive between the motor and compressor, but may. join the compressor and motor with a shaft, end to end, for direct drive as through a flex ible coupling or the like. The circuit of the motor is controlled by pressure regulator 8 which connects the motor and disconnects the motor to and from a source of current, as i well understood by those skilled in the art.

The compressor has a cylinder frame 10 in which there mounted a sleeve valve 11 operated preferably by ring friction of the piston, the dome of which is shown at 12 in l igure 2. 'lhe cylinder frame 10 has a head 18 bolted thereto, as by means of the bolts 14;, and this head has a conical discharge pa eway 15 extending therethrough. A neck 16' is formed integral with the head 13 and it continued up to form a seat- 17 for the discharge check valve 18, and then contin ued on upwardly in the shape of a flaring flange or funnel 19. The check valve 18 is held to its seat by a spring 20 held in a cage 21, which cage is open into the lower part of the funnel and hence opened directly into the tank or receiver 22, which tank or receiver is mounted directly upon the head by a fluid tight joint. The tank is provided with an opening surrounded by a flange fitting 23,

which is clamped to an extending flange 24 formed on thehead member 13.

The tank 22 is preferably a cylindrical tank laidon its side so as to be clamped to the head 13, as above described, and supported at its other end by a post or bracket 26 on the base 2. 'l he tank is secured to this bracket 26 by means of a hoop bolt 27, wiiich partially embraces said tank and is secured to lugs or cars on the bracket 26 in a well known man ner. .he tank provided with a discharge connection 28 which leads to the point of consumption of the compressed air. A drain valve 29 is provided in the bottom of the tank, and this drain valve has a nipple 30 extending a short distance above the bottom of the tank for the purpose of retaining a body of water 31 in the bottom of the tank and in the well 32 which is formedbythehead l3 and the surrounding flange 23 fastened on "the bottom side of the tank 22. A pressure ronnection consisting of a small pipe 33 er:- tends into the tank at a point well above the water level and leads through a paclred or sealed opening 3-1 to a pipe 35, which is 3011- nected to the pressure regulator 8 so that when pressure in the tank 22 rises to a predetermined value the regulator 8 cuts off the current supply, stopping further compres- S1011.

The tank 22 is provided with a connection incluiding a gauge 36 and a safety valve 37 of the well known pop type.

in operation, the compressor 1 is driven by the motor 3 when the pressure in the tank 22 is below the predetermined minimum, air being taken in about the top of the sleeve valve 11 and drawn into the interior of the same, which forms the cylinder in which the piston plays, and upon the discharge stroke the sleeve is first raised to contact with a yielding annular plate which forms the sleeve valve seat and then the air is forced out the discharge passageway 15, opening the check valve 18 and passing out through the openings in the cage 21 into the open funnel or discharge conduit formed by the conical flange 19. It is desirable to keep the water out of the discharge check valve cage so that if the check valve leaks. no water escapes back into the cylinder. ater in the cylinder would be injurious to the compressor under operation. The funnel 19. therefore, permits the air as soon as it is discharged to mingle with the contents of the tanl-z 2" which. in the present instance, consists of compressed air at a relat'vely low temperatiufe.

T be hot compre sed air discharged by the piston into the tank 22 tends to rise by gravity, or by differences in gravity, to the top of the tank 22 where it moves longitudinally in contact with the top wall, distributing itself thereover, both because of the velocity with which it enters and because of the difference ingravity between cold and hot air and,

as a result, the top of the tank is hotter than the bottom. This is desirable since it immediately removes the heated gases from the proximity of the cylinder and discharge valve.

At the same time the body of water in the bottom of the tank tends to keep the head cool and it tends to circulate also. By this circulation it is possible to carry the water which is heated by the head and discharge passageway to a remote point where the same tends to radiate or otherwise give off its heat and return by gravity,

This body of water is capable of performing another function, namely, the rapid transfer of heat from the compressor to the relatively large surface of the tank. In case the water runs so hot as to begin to vaporize by ebullition the vapor travels to the walls and is condensed and runs down the sides of the walls back into the bottom of the tank, there by quickly transferring heat and dissipating the same much more rapidly than would be the case by more convection of the air. This system, therefore, has a certain characteristic of residual safety in that when the water is brought to the boiling temperature, that is, a temperature of rapid vaporization, it is ca pahle of throwing off heat through the walls 22 at a much higher rate, so that if the water should reach the boiling point at the pressure corresponding to that at which the tank 22 is operated it can throw off heat much more rapidly than theretofore, so that the temperature of the head is definitely limited.

However, the chief function of cooling and the normal mode of operation is that an incoming charge of hot compressed gas is immediately diluted in the large pool of gas which is held under pressure in the tank 22. A part of the mixture is drawn oil at the dis tributing main 28 in the normal course of the use of the compressed air, and the remainder is cooled off and the cooler part sinks to the bottom and the next charge of hot compressed gas is again mixed, rises to the top, cools, and descends'in an orderly circulation.

If. due to the cooling and compression, more moisture is brought into the tank than is d-taired, the excess may be removed by open ing or partially opening the valve 29, whereupon the level will be brought down to the top of the nipple or standpipe 30.

I do not intend to be limited to the details shown or described, except as they appear in the follo\\"ing claims.

I claim i. In a gas compressor, the method of limiting the temperature rise of the discharge check valve which comprises discharging a charge of hot compressed gas past said check valve into a relatively large diluting volume of gas at substantially the same pressure but at lower temperature.

2. In a gas compressor, the method of lim iting he temperature rise of the discharge check valve which comprises discharging the charge of hot compressed gas past said check valve into a relatively large diluting volume of gas at substantially the same pressure but at lower temperature, and withdrawing heat from the mixture so formed.

3. The method of limiting the temperature rise of the discharge check valve of a compressor which comprises discharging the in dividual charges of hot compressed gas past said check valve into a relatively large pool of gas at substantially the same pressure and at lower temperature, withdrawing a portion of said mixture, and cooling the remainder of the mixture to dilute the succeeding charge.

1. In combination, a compressor having a cylinder head, a neck extending therefrom, a discharge passageway through said neck, a check valve at the other end of the neck controllin said passage, and a tank of relatively large volume and heat dissipating capacity connected to said head about said neck, said check valve opening directly into said tank.

5. In combination, a compressor having a head, a discharge passageway through the head, a check valve controlling said passage way, a chamber of large volume communicate ingwith said passageway under the control of said valve, said valve being exposed freely to the contents of said chamber, said chamber having sutlicient cooling area to dissipate the heat of the. compressed gas and thereby maintain the temperature of the valve below the carbonizing pointof lubricating oil.

6. In combination, a compressor having a cylinder, a head, and a central discharge pas- :geway through the head, a check valve controlling said passageway, a chamber of relatively large volume secured to the head about the check valve, and an annular flange extending above the check valve and serving to direct the gas discharged. from the cylinder towards the top of the chamber.

7'. In combination, a compressor having a cylinder, a head therefor, said head having a neck extending therefrom, said neck having a discharge passageway from the cylinder therethrough, aid head having a bottom flange extending beyond the cylinder, a tank having a hole in its wall, a companion flange secured to the tank about said hole and bolted to the head flange, said neck projecting into the tank through the hole therein, and a check valve governing the discharge passageway.

8. In combination, a compressor having a cylinder, a head therefor, said head having a neck extending therefrom, said neck having a discharge passageway from the cylinder therethrough, said head having a bottom flange extending beyond the cylinder, a tank having a hole in its wall, a companion flange secured to the tank about said hole and bolted to the head flange, said neck projecting into the tank through the hole therein, a check valve governing the discharge passageway, a gas director about the check valve secured to said neck, and a body of cooling liquid lying in the tank in contact with said head and neck.

9. In 'ombination, a compressor having a cylinder,'a head therefor, said head having a neck extending therefrom, said neck having a discharge passageway from the cylinder therethrough, said head having a bottom flange extending beyond the cylinder, a tank having a hole in its wall, a companion flange secured to the tank about said hole and bolted to the head flange, said neck projecting into the tank throu h the hole therein, a check valve governing the discharge passageway, a gas director about the check valve secured to said neck, a body of cooling liquid lying in the tank in contact with said head and neck, and means for drawing ell an excess of liquid from said tank above a predetermined level.

10. The method of limiting the temperature rise of the head and discharge check valve of a con'ipressor which con'iprises discharging the charge of compressed gases at each stroke into a pool of compressed air of substantially the same pressure, vaporizing a body of liquid in thermal contact with said head and check valve and 1 ii-zing said vapor with the. pool o'l' compresed air, dissipating the heat from said pool of compressed air and the contained vapor to cool the air and condense said vapor, and returning the condensate by gravity within the pool of compressed air into thermal contact with the head and valve.

11. In combination, a base plate,acompressor mounted on said base plate, a motor for driving the compressor also mounted on the base plate, said con'ipressor having a head, a flange on the head, a discharge passageway through the head, a tank having an opening and having a flange surrounding the opening, said flange being secured to the flange of the compressor head, and a bracket mounted be tween the base and the tank for supporting a part of the weight of: the tank, the discharge passageway ot the compressor opening into the interior of the tank.

12. In a compressor, the method of limiting the ton'iperature rise of the discharge valve which comprises discharging the charges 0t hot gas past said valve into a large body of cool gas at substantially the same pressure and then transferring heat received by said discharge. valve from contact with the hot gases to the mixture.

13. In combination, a compression cylinder having a head, the head having a discharge pr range, a check valve for the passage, a tubula r shell surrounding the check valve, said tubular shell having a seat therein for the check valve, and a casing providing a chamber about the tulnilar shell and providing a pocket for liquid upon the cylinder head, said casing and tubular shell being in communication to permit the compressed air to pass into the chamber.

In a gas compressor, the method of limiting the ten'iperature rise of the discharge check valve which consists in surroun ding the dis-scharge check valve with abody of liquid contained in a receiver having sutlicient radiating surface to keep the liquid cool enough to hold the discharge check valve below the temperature of ca-rbonization of oil.

15. In a compressor, a discharge check valve, and a casing surrounding the valve and containing a body of liquid for cooling the dis-:charge check valve, said casing having sufiicient radiating surface to keep the liquid cool enough to hold the temperature of the discharge check valve below the temperature of carbonization of oil.

16. The method of limiting the temperature "1e oil. the head and discharge check valve of a compressor which comprises discharging the charge of compressed gases: at each stroke into a pool of compressed air of substantially the same pressure, vaporizing a liquidv in thermal contact with said head and check valve and mixing said vapor with the pool of compressed air, dissipating the heat from said pool of compressed air and the contained vapor to cool the air and condense said vapor, and returning the condensate into thermal contact with the head and valve.

In witness whereof, I hereunto subscribe my name this 1st day or April, 192?.

BURTQN S. AllIMrrN. 

